My world is gone

Hey, I don't understand what happened. I was about to enter my world till My xbox shut down then it back to on. I went to Minecraft to check out, I saw my world (Creativity World) is gone. I was like what's going on?! I've been working so hard through my world about a few weeks, now it's gone! HOW I GET MY WORLD BACK?! Please help me to get my world back! I am so upset, I spend all of my time in my world to create everything. I want my world back... Creativity World is one of my worlds, I have five of them but now I have four worlds because of my world (Creativity World) got deleted for no reason..My world named "Creativity World" is 5th world but it's gone for unknown reason, I want that world back.